Field
Embodiments described herein relate generally to a semiconductor memory device and a manufacturing method thereof.
Description of the Related Art
As one of a semiconductor memory device, there has been provided a flash memory. In particular, since its inexpensiveness and large capacity, a NAND flash memory has been generally widely used. Up to the present, many techniques to further increase the capacity of this NAND flash memory have been proposed. One of the techniques is a structure of three-dimensionally disposing memory cells. In such three-dimensional semiconductor memory device, the memory cells are disposed in a laminating direction. Conducting layers extend from the respective memory cells, which are disposed in the laminating direction. Such conducting layers extend in a horizontal direction with respect to a substrate and are laminated in the vertical direction with respect to the substrate.
With such three-dimensional semiconductor memory device, an increase in the numbers of laminated layers of the memories and the conducting layers increases an area of a contact area (a stepped portion), which is to extract the conducting layer to the outside.